Cancer is a disease that results from abnormal growth and division of cells
that make up the body's tissues and organs. Under normal circumstances,
cells reproduce in an orderly fashion to replace old cells, maintain tissue
health and repair injuries. However, when growth control is lost and cells
divide too much and too fast, a cellular mass -or "tumour" -is
formed.
If the tumour is confined to a few cell layers and it does not invade surrounding
tissues or organs, it is considered benign. By contrast, if the tumour spreads
to surrounding tissues or organs, it is considered malignant, or cancerous.
In order to grow further,
a cancer develops its own blood vessels and this process is called angiogenesis.
When it first develops, a malignant tumour may be confined to its original
site.
If cancerous cells are not treated they may break away from the original
tumour, travel, and grow within other body parts, the process is known as
metastasis.

Lung cancer is a growth of abnormal cells inside the lung. These cells
reproduce at a much faster rate than normal cells. The abnormal cells
stick together and form a cluster or growth, known as a tumour. If the
abnormal cells began growing in the lung, this is known as a primary lung
tumour.

Types of lung cancer

Cancers that begin in the lung are divided into 2 major types:
non-small cell lung cancer and small cell lung cancer, depending
on how the cells look under a microscope. Non-small cell lung cancer generally
spreads to other organs in the body at a slower rate than small cell lung
cancer. Non-small cell lung cancer is the most common type of lung cancer,
accounting for almost 80 per cent of lung cancers. Small cell lung cancer
accounts for about 20 per cent of all lung cancers.

Causes

Cigarette smoking is the major cause of lung cancer. Up to 90 per
cent of cases of the disease are caused by smoking, and one in 10 smokers
will develop lung cancer. The longer a person has been smoking and the
more packs of cigarettes smoked per day, the greater the risk. However,
it is not known why one smoker develops lung cancer while another does
not.

Workers exposed to industrial substances such as asbestos, nickel, chromium
compounds, arsenic, polycyclic hydrocarbons and chloromethyl have a significantly
high risk of developing lung cancer.

Research has also demonstrated the link between passive smoking and lung
cancer.

Symptoms

Lung cancer is very difficult to detect at an early stage. Common
symptoms include: a new or changing
cough, along with hoarseness or shortness of breath or increased shortness
of breath during exertion; and

recurring episodes
of lung infection, weight loss and swelling of the face or arms.

Treatment

There are various treatment options for lung cancer (with different
aims), including: surgery; chemotherapy; radiotherapy; and laser treatment.

Those non small cell lung cancers which are amenable to surgery are those
where the cancer is confined to a lump in the lung or to the draining
lymph nodes immediately next to the lump, but disease where the lymph
nodes in the centre of the chest are involved is usually considered not
suitable for surgery alone. Investigations include chest x-rays and CT
scans. Surgery may involve removal of all the lung or part of the lung.
For those cancers that spread to the centre of the chest, a combined treatment
approach may involve chemotherapy with radiotherapy and surgery. Patients
who present with widespread disease or later develop widespread non small
cell lung cancer may have chemotherapy which improves the chance of 12
months survival by 9%.

Radiotherapy is used to alleviate the symptoms from the primary cancer
or other sites of disease, such as the bone.

Small cell lung cancer is primarily treated with chemotherapy. The best
outcome is if the disease is confined to the chest but chemotherapy is
still used in disease that is widespread at presentation. Radiotherapy
may be used to consolidate the local chest area or to prevent metastases
occurring in the brain. Radiotherapy can also be used for palliation of
painful localised areas, such as in the bone.